A new project was initiated on the analysis of mutagenicity of 155 chemicals that were tested by the EMTDP Laboratory for mutagenicity using the Salmonella test and grouped according to structural similarities. Other activities included compiling toxicological data for insertion in data base records and profiles of chemicals identified in wast dumps throughout the United States; collecting and documenting carcinogenicity information for the NTP Annual Reports on Carcinogens; and compiling information on chemical/chemical interactions, chromosome breakage and/or sister-chromatid exchange in human cells, and the mechanism of action of oncogenes.